1. Field of the Invention
The present invention relates to a door or tailgate for vehicle such as a pickup truck, having a torsion bar for assisting the closure of the tailgate.
2. Disclosure Information
Tailgates used with large pickup trucks present a challenge to the operator of the truck insofar as the weight of such tailgates and the height of such vehicles frequently result in the necessity of expending considerable effort to close the tailgate. U.S. Pat. No. 5,358,301, which is shown in FIG. 6, discloses a torsion bar system for assisting the closure of a tailgate. Unfortunately, the system disclosed in the ""301 patent suffers from several drawbacks. First, the system would have high cost because the torsion bar is itself used as a hinge pin and this necessitates that the torsion bar be sufficiently large to not only function in torsion, but also in shear so as to support the tailgate itself. Secondly, the fact that the torsion bar functions not only as a torsion element but also as a pivot for tailgate means that in the event that the torsion bar breaks, the tailgate""s pivot function may be impaired, with the result that the tailgate could separate from the vehicle in a unwanted manner.
A torsion bar tailgate lift assist system according to the present invention solves the problems inherent in the previously described system, but at a lower cost, while providing a torsion bar which is full floating. This means that if the torsion bar of the present inventive system were to break, the pivoting function and retention of the tailgate to the body of the pickup truck would not be adversely affected.
An automotive closure panel includes a door, typically a tailgate adapted to pivot about a generally horizontal pivot axis, with the door having a shell defining an interior space. A first hinge bearing retainer is attached to a first end of the door and has a first bearing insert housed within the retainer. A first pivot post is rigidly attached to a structure such as a side pillar adjoining a first end of the pivot axis, with the pivot post engaging a bore formed in the interior of the said first bearing insert. A second hinge bearing retainer is attached to the second end of the door and has a second bearing insert housed therein. A second pivot post is rigidly attached to a structure such as a second side pillar adjoining a second end of the pivot axis. The second post engages the second bearing insert such that the second pivot post and the second bearing insert are rotationally locked. This means as the tailgate is pivoted, the second bearing insert will rotate within the second bearing retainer. In other words, the second bearing insert will rotate with respect to the second bearing retainer because the second bearing insert will not rotate at with respect to the tailgate. This means that the tailgate itself, including the second bearing retainer, will rotate about the second bearing insert.
The present automotive closure panel further includes a full floating torsion bar having a first end rotationally grounded within the interior of the door, and a second end engaged with and rotationally locked with the previously described second bearing insert such that the torsion bar will be subjected to torsional loading as the door is pivoted. The second pivot post is oriented so that the torsion bar is subjected to a minimal torsional load tending to open the door when the door is in a closed position. The orientation of the second pivot post further allows the torsion bar to be subjected to a maximum torsional load tending to close the door when the door is in a fully open position, which normally corresponds to about 90Âxc2x0 of rotation from the closed position.
The torsion bar of the present system is situated such that the first end of the torsion bar is grounded within an anchoring member located within the interior of the door, wherein the anchoring member passes through an aperture of the door shell during assembly. The anchoring member may take a variety of forms such as a bracket, mounting block, or a pinch block. The anchoring member may be affixed to a portion of the first bearing retainer via a hinge bracket or the like, or directly to the first bearing retainer.
The first bearing insert and first pivot post are keyed in a manner used with 2003 model year pickup trucks produced by Ford Motor Company, so as to allow the closure panel to be removed from a vehicle when the panel has been opened to a predetermined position.
According to another aspect of the present invention, a method for constructing an automotive tailgate includes the steps of fabricating a door adapted to pivot about a generally horizontal pivot axis, with the door having a shell defining an interior space, and with the shell having a first end and a second end, and attaching first and second bearing retainers to the shell, with each of the bearing retainers housing a bearing insert. The present method further includes providing a first pivot post rigidly attached to a body structure adjoining a first end of the door shell when the door is in a closed position. The first pivot post engages a bore formed the interior of said first bearing insert. A second pivot post is attached to a pillar structure adjoining the second end of the door when the door or tailgate is in a closed position, with the second pivot post engaging the second bearing insert such that the second pivot post and second bearing insert are rotationally locked.
According to another aspect of the present invention, a cargo box for an automotive vehicle includes left and right pickup box sides, a first side pillar attached to the right pickup box side, and a second side pillar attached to the left pickup box side. A first pivot post is attached to the first side pillar, and a second pivot post is attached to the second side pillar. A tailgate is hingedly attached to the first and second pivot posts, with the tailgate having a full floating torsion bar lift assist. The torsion bar has a first end rotationally grounded within the interior of the tailgate, and a second end rotationally locked with the second pivot post such that the torsion bar will be subjected to torsional loading as the tailgate is pivoted to an open position.
Finally, according to the present invention, a full floating torsion bar is provided, with the bar housed entirely within the interior space of the door and with the torsion bar having a first end rotationally grounded within the interior of the door and a second end engaged with and rotationally locked with the second bearing insert such that the torsion bar will be subjected to torsional loading as the door is pivoted.
It is an advantage of the present invention that an automotive tailgate may be provided with a lift assist system having less weight than other known lift assist systems.
It is a further advantage of the present invention that the present lift assist system is less costly than known lift assist systems.
It is a further advantage of the present invention that the present lift assist system will not impair the basic functions of the tailgate even if the torsion bar should fail during normal operation of the vehicle.
It is a further advantage of the present invention that the torsion bar employed in the inventive lift assist system may be readily changed in diameter, or in length, or both, so as to alter the effective spring rate of the torsion bar, without the necessity of retooling the tailgate hardware. This change is not easily accommodated by prior art designs.
It is a further advantage that a vehicular door, such as a tailgate, equipped according to this invention has a self-contained torsion bar mechanism, allowing the tailgate to be removed without the use of tools.
Other advantages, as well as objects and features of the present invention, will become apparent to the reader of this specification.